The issue began when I installed Visual Studio 2011 Ultimate Beta and selected a Web Developer layout. I later went in and reset my settings to be the C# default layout. When I selected the Dark Theme (which I’ve now become quite used to) the UI itself switched fine but the code window still had the Light theme colors! Here is a screenshot to illustrate what I mean:

Doing a quick search I came across this excellent MSDN forums post that had a solution. The good news is that it is a known bug in the current Beta release and will be fixed before launch.

This brought the dark theme back for me but upon selecting a bigger font size the IDE reset itself and went back to the Light Theme. I then closed Visual Studio, switched to Dark Theme (Tools –> Options – > Environment –> General –> Visual Experience –> Color Theme), changed the font size and everything was back to normal!

That should hopefully fix it for you!

If you are currently working on a Windows 8 app I would love to hear about it. You may also want to check out my previous Windows 8 Metro Style Development Tips: